It's going to be trial and error...confirm timing , fuel mixture ( too lean - check and " read" plugs) , fuel pressure ( 1.5 to 2 lbs ) balance tube is necessary on the dual EMPI 34's and won't hurt to add it to the Kadrons. Fuel line to heat source issues ? Valves pinging ( rattling ) under load? How hot is the engine getting? Can you pull the oil dip stick and hold it with your fingers ? If you can't it's running hot. May try propping the rear deck lid and inch or so and see if that resolves the run issue.